<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="text">
<div>1</div>
<div>2</div>
<div>3</div>
<script src="https://cdn.staticfile.org/jquery/2.1.1/jquery.min.js"></script>
<script>
    $("input").val("内容被修改了")
    $("div:first").text("找到了1")
    $("div:eq(1)").text("找到了2")
    $("div:last").text("找到了3")
    let h = $("<h1>我是h1</h1>")
    $("body").append(h)
    $("div").css("color","red");
    console.log($("div").css("color"))
</script>
</body>
</html>